The present invention contemplates equipment for treatment of various localized tumors such as prostate, rectal, cervical or uterine. The term "tumor" as used herein refers to any abnormal tissue growth. In fact, the invention may be used for any temperature sensitive tumor. The present invention will be described with regard to a typical type of tumor suitable for treatment with the equipment of the present invention, namely, prostate cancer.
Prostate cancer is the second most common cancer in males in the United States, and the third most common cause of male cancer death. In 1986, an estimated 90,000 men in the US were diagnosed with prostate cancer, and 26,100 death from the disease were estimated to have occurred.
Age has a major impact on the incidence of prostatic cancer. The disease is uncommon in men younger than age 50, but the incidence increases sharply to more than 1,000 per 100,000 man-years for American males age 85 and over. The average age of prostate cancer patients at the time of diagnosis is 73 years. For males over the age of 75, mortality due to prostate cancer is exceeded only by lung cancer. Relative to other forms of malignancy, this disease accounts for 21 percent of newly diagnosed cancers in males and 11 percent of cancer deaths.
Many factors are involved in choosing treatment modes for the individual patient. Those factors are patient age and anticipated life expectancy, associated medical problems, sexual potency, potential complications of therapy, and, ultimately, consideration for quality of life with and without therapy.
In choosing appropriate treatment options cost factors have been largely ignored in the past. The cost, including physician fees, of perineal prostatectomy is substantial with typically 8.0 hospitalization days required. The delivery of external radiation therapy for localized prostate cancer according to the present invention may be a 6-weeks-course on an outpatient basis. Treating patients with the method of the present invention, e.g. hyperthermia delivered on an outpatient basis would lead to a reduction of hospital days associated with surgery. In the context of radiation therapy effective hyperthermia can enhance the effect of radiation and result in a higher local cure rate.
Traditionally radical prostatectomy has been widely employed on otherwise healthy men with clinical Stage A or B and occasionally small Stage C lesions. Limitations in success in treatment stem from inaccurate clinical staging which fails to predict extraprostatic carcinomatous spread prior to surgery.
Despite numerous refinements in surgical technique, the role of prostatectomy for patients with histological evidence of extracapsular disease remains uncertain. Attempts to treat residual cancer following incomplete resection evidenced by histological demonstration of capsular penetration, involving surgical margins or seminal vesicels, have focused primarily upon external beam irradiation techniques administered in the period following total recovery from surgery.
Radiotherapy, like surgery, offers a patient the possibility of local-regional control of prostatic carcinoma. External beam radiation has generally been given to the prostate in doses of 5,500 to 7,000 rads. Perez et al. have reported a failure rate of 18.5% in patients who received 7,000 rads to the prostate. Cupps and associates found a 14% rate of local recurrence by digital examination in patients who had received external-beam radiation; in stage B disease, they observed a 20% combined local and systemic failure rate, whereas the combined failure rate for stage C disease was 49%. Lupu and associates have reported a 32% five-year local failure rate for stage C lesions treated with external radiation alone. Gibbons et al. have found a 92% local clinical control rate for stage C carcinoma of the prostate with external radiation alone, but they define local control as lack of requirement of further surgery for obstruction or bleeding. Other investigators have observed that postradiation biopsy continues to be positive for residual tumor in 40% to 70% of patients treated with external-beam radiation. Unfortunately, the determination of local clinical control has in the past relied on digital examinations and not on sensitive serum markers and ultrasonic rectal follow-up checks. Local tumor recurrence or persistence has nevertheless been associated with a higher incidence of systemic failure. These findings would lead to suggest modalities to increase the effectiveness of radiation with the use of adjunct hormonal or chemotherapy treatment or with the use of hyperthermia.
Interstitial radiation therapy with iodine isotope (I-125) has been reported to carry a 16% incidence of local failure in patients with stage C disease followed five years. Scardino et al., however, observed an incidence of positive postradiation biopsy of 50%. Local tumor recurrence using a combination of radical surgery and interstitial gold isotope (AU-198) has been reported in the range of 4% to 8%.
Since 1866, when Busch published the first scientific report of a regression of a histologically proven sarcoma following an attack of high fever caused by erysipelas, many authors have reported the disappearance or regression of tumors by hyperthermia therapy.